Add explicit type annotations to nullable columns

TypeORM can't correctly infer the data type on properties with a `| null` type.
This commit adds explicit type annotations.

See also https://github.com/typeorm/typeorm/issues/2567#issuecomment-408599335

Signed-off-by: David Mehren <git@herrmehren.de>

src/notes/note.entity.ts

@@ -35,6 +35,7 @@ export class Note {
   @Column({
     unique: true,
     nullable: true,
+    type: 'text',
   })
   alias: string | null;
   @OneToMany(
@@ -70,10 +71,12 @@ export class Note {
 
   @Column({
     nullable: true,
+    type: 'text',
   })
   description: string | null;
   @Column({
     nullable: true,
+    type: 'text',
   })
   title: string | null;